Wait to get a ray until your 210 is set up. They are a huge load on your bio filter, and having one established is a must. Be prepared to upgrade your 210, especially if you have a female motoro. I've kept my rays on bb and sand, but as posted earlier, do fine on gravel. IF, by teacup, you are referring to, are retics, they are just as hardy as any other ray as long as its healthy to beging with! They would last a lot longer (if not for life) in your 210 than a motoro. Just some advice, I just got a large female about 16-18" disc and it makes my 3ft wide tank look a lot smaller than I had thought!